Source-backedFixed AnnualIn-depth guide
World Thrombosis Day
International Society on Thrombosis and Haemostasis (ISTH)
Observance library
Browse all researched observances
2,411 researched observances. Search for a specific name or known alternate name.
Source-backedFixed AnnualIn-depth guide
World Thyroid Day
European Thyroid Association and sister thyroid associations
Source-backedFixed AnnualIn-depth guide
World Tofu Day
SPA Canada creator-side material states that it launched the first World Tofu Day edition in Montréal in 2014; a contemporaneous Montréal account identifies July 26, 2014 as the first celeb…
Source-backedFixed AnnualIn-depth guide
World Toilet Day
A/RES/67/291
Source-backedFixed AnnualIn-depth guide
World Tourism Day
UN Tourism observance
Source-backedFixed AnnualIn-depth guide
World Town Planning Day
American Planning Association material states that Carlos María della Paolera started World Town Planning Day in Buenos Aires in 1949 and that it is observed every 8 November.
Source-backedFixed AnnualIn-depth guide
World Tsunami Awareness Day
A/RES/70/203
Source-backedFixed AnnualIn-depth guide
World Tuberculosis Day
WHO observance
Source-backedFixed AnnualIn-depth guide
World Tuna Day
A/RES/71/124
Source-backedFixed AnnualIn-depth guide
World Turkic Language Family Day
UNESCO 43 C/57
Source-backedFixed AnnualIn-depth guide
World Turtle Day®
The official World Turtle Day site states that American Tortoise Rescue founded the observance in 2000 and that World Turtle Day is held annually on May 23; its 2026 release marks the 26th…
Source-backedRule Based AnnualIn-depth guide
World Usability Day
World Usability Day identifies Elizabeth Rosenzweig as founder/director, documents its 2005 first year and second-Thursday-in-November recurrence, and maintains a live 2026 program; its arc…
Source-backedFixed AnnualIn-depth guide
World Vegan Day
The Vegan Society states that World Vegan Day takes place annually on 1 November and was created in 1994 for the Society’s 50th anniversary.
Source-backedFixed AnnualIn-depth guide
World Vegetarian Day
NAVS states that World Vegetarian Day was established as an annual celebration, with 1 October as the official date; local events may be scheduled on a nearby date.
Source-backedRule Based AnnualIn-depth guide
World Veterinary Day
The World Veterinary Association states that it created World Veterinary Day in 2000 for annual observance on the last Saturday of April and continues to lead the campaign, including 25 Apr…
Source-backedFixed AnnualIn-depth guide
World Voice Day
World Voice Day Committee and international voice-health community
Source-backedFixed AnnualIn-depth guide
World Water Day
A/RES/47/193
Source-backedFixed AnnualIn-depth guide
World Water Monitoring Day
U.S. EPA material documents the inaugural World Water Monitoring Day in 2003 as coordinated by America’s Clean Water Foundation and the International Water Association, originally centered…
Source-backedFixed AnnualIn-depth guide
World Wetlands Day
A/RES/75/317
Source-backedRule Based AnnualIn-depth guide
World Wide Knit in Public Day
The National NeedleArts Association lists World Wide Knit in Public Day on the second Saturday in June, and a U.S. National Park Service 2026 event confirms the June 13, 2026 edition.
Source-backedFixed AnnualIn-depth guide
World Wildlife Day
A/RES/68/205
Source-backedFixed AnnualIn-depth guide
World Wish Day
Make-A-Wish International verifies World Wish Day on April 29, its connection to the April 29, 1980 wish that inspired the movement, and continuing global stewardship in 2026; the exact fir…
Source-backedFixed AnnualIn-depth guide
World Youth Skills Day
A/RES/69/145
Source-backedFixed AnnualIn-depth guide
World Zoonoses Day
FAO identifies 6 July as World Zoonoses Day and ties the date to the first successful rabies vaccination on 6 July 1885; a modern founder/first formal edition is not established.
Source-backedRule Based AnnualIn-depth guide
Worldwide Pinhole Photography Day
The organizer states that WPPD is held on the last Sunday in April; the official archive reaches back to 2001, and founding-history sources identify 29 April 2001 as the first edition after…
Source-backedFixed AnnualIn-depth guide
Wright Brothers Day
36 U.S.C. §143 designates December 17 as Wright Brothers Day and states that it commemorates the first successful heavier-than-air mechanically propelled airplane flights by Orville and Wil…
Source-backedFixed AnnualIn-depth guide
YMA Day
Young Mizo Association history dates its founding to 15 June 1935; Mizoram government sources continue to mark 15 June as YMA Foundation Day, and reviewed state holiday calendars list YMA D…
Source-backedFixed AnnualIn-depth guide
Yorkshire Day
Yorkshire Ridings Society material states that the Society first organised Yorkshire Day in 1975 and chose 1 August for the Minden/white-rose connection; government and current civic materi…
Source-backedFixed AnnualIn-depth guide
Zero Discrimination Day
UNAIDS observance
Source-backedRule Based AnnualIn-depth guide
Zero-Tasking Day
Creator Nancy Christie says she created Zero-Tasking Day in 2005 around the U.S. return to standard time; current creator-profile and contemporaneous publisher material support the first-Su…
Source-backedFixed AnnualIn-depth guide
ZIP Code launch anniversary
USPS states that Postmaster General J. Edward Day announced the ZIP Code would launch on 1 July 1963.
Source-backedRule Based AnnualIn-depth guide
Zoo Awareness Weekend
Freedom for Animals states that it holds Zoo Awareness Weekend every year and places it on Easter Weekend because that period is typically busy for zoos.
Source-backedFixed AnnualIn-depth guide
Ólavsøka / Saint Olaf's Wake
The official Faroe Islands site verifies Ólavsøka as the July 28–29 national festival, July 29 as the National Day, and the Saint Olaf historical rationale. Claims remain scoped to the Faro…
Source-backedFixed AnnualIn-depth guide
“In God We Trust” coinage anniversary
U.S. Mint and Library of Congress history identify 22 April 1864 as the date Congress authorized the motto on the two-cent coin. That supports an anniversary anchor; it does not establish a…
Source-backedFixed AnnualIn-depth guide
“OHI” Day / 28 October anniversary
Hellenic Ministry of Foreign Affairs